1. Field of the Invention
The present invention particularly relates to an image pickup unit for an endoscope which is contained in a distal end portion, in image pickup units for endoscopes provided in electronic endoscope apparatuses.
2. Description of the Related Art
In recent years, endoscopes have been widely utilized in a medical field and an industrial field. In conventional endoscopes, image guides have been used, and endoscopes which enable users to observe insides of body cavities of patients, inner portions of jet engines or the like in eyepiece portions which users look into have been typical.
Further, in recent endoscopes, an electronic endoscope apparatus has appeared, in which an image pickup unit provided with a solid image pickup device is incorporated in a distal end portion of an insertion portion, photographs the inside of the body cavity of a patient, the inner portion of a jet engine or the like, and displays an endoscopic image on a display apparatus such as an external monitor.
The image pickup unit of the electronic endoscope apparatus is provided with an image sensor which photoelectrically converts detected light into an electric signal. As the image sensor, the image sensor with a solid image pickup device, an electronic circuit and the like being packaged as one electronic component has been typical.
Further, the image pickup unit for use in an electronic endoscope is required to have such a size as to be capable of being housed inside of a downsized distal end portion with reduction in a diameter of an insertion portion. Therefore, some of the image pickup units placed in the distal end portions of endoscope apparatuses with small housing spaces use prisms as structures which cause refracted lights to be incident on image sensors, in order to prevent the distal end portions from being upsized in an outside diameter direction in particular.
For example, Japanese Utility Model Application Laid-Open Publication No. 5-9504 discloses a technology of a solid image pickup device package that has a holding member which holds a barrel and a prism which are integrated, and completely prevents separation of a cover glass and a package body made of ceramics by the holding member. In the solid image pickup device package described in the Japanese Utility Model Application Laid-Open Publication No. 5-9504, the package body of ceramics, and the holding member formed from a metal material or a synthetic resin material are used.
Incidentally, light shielding ability for unnecessary light to a light receiving element is required for an image pickup unit so that a light other than a photographing optical image is not detected in the light receiving element of the solid image pickup device.